Adjustable plumb bob



Sept. 29, 1959 o. JOHNSON 2,905,033

ADJUSTABLE PLUMB BOB Filed March 25, 1958 47 fix OSCAR JOHNSON INVENTOR ATTORNEY United States Patent ADJUSTABLE PLUMB BOB Oscar Johnson, Springfield Gardens, N.Y.

Application March 25, 1958, Serial No. 723,861

2 Claims. (Cl. 33-217) This invention relates to plumb bobs and, more particularly, to a weighted plumb bob having support means of adjustable length.

A considerable amount of time is frequently wasted in winding up the string ordinarily used to support a plumb bob in actual use. In many cases, the string often becomes entangled during use and while being stored, thus further inconveniencing and hampering the particular operation. It is therefore an object of the present invention to provide an adjustable plumb bob having self contained means for controlling the length of the support string extending outwardly therefrom, which plumb bob is extremely simple in construction, efficient in operation, and which will overcome the aforementioned difliculties.

Another object of the present invention is to provide a compact adjustable plumb bob having a self contained reel or drum upon which the supporting string is wound until ready for use, a manually operated brake or clutch mechanism being provided to enable the string to be unwound from such drum.

Still a further object of the present invention is to provide an adjustable plumb bob of the type described having associated winding apparatus for frictionally rewinding the string upon the drum.

All of the foregoing and still further objects and advantages of this invention will become apparent from a study of the following specification, taken in connection with the accompanying drawing, wherein:

Figure l is a perspective view of a plumb bob made in accordance with the present invention;

Figure 2 is a fragmentary side elevational view taken along line 2-2 of Figure 1;

Figure 3 is a fragmentary front elevational view taken along line 3-3 of Figure 2;

Figure 4 is an enlarged fragmentary longitudinal cross sectional view taken along line 4-4 of Figure 1;' and Figure 5 is an enlarged fragmentary side elevational view, with parts broken away, of a plumb bob made in accordance with the present invention in actual use.

Referring now to the drawing, a plumb bob made in accordance with the present invention is shown to include a main weighted body member 12 having a point 13 at the lower end thereof. The upper end of the main body member 12 is provided with an internally threaded longitudinal bore 16 within which a threaded plug is secured. A threaded shaft 18 is also threadedly engaged with the longitudinal bore of the plug 15 and is secured in place therewith by means of a lock nut 19. A drum 20 having a longitudinal bore 21 is rotatably supported upon the shaft 18 for rotation about the longitudinal axis of the main body member 12.

The lower end of the drum 20 is provided with a radially outwardly enlarged flange 23 having a resilient rim 24 peripherally secured thereto. The upper end of the drum 20 is provided with a smaller flange 25 so as to define a sheave 27 upon which a substantially long length of string 28 may be wound. A cap nut 30 threadedly engaged with the upper end of the shaft 18 and lock 2,906,033 Patented Sept. 29, 1959 thereon by means of a lock nut 31 so as to define the upper limit of movement of the drum 20. The upper terminal portion 33 of the shaft 18 is tapered and is provided with a substantially J-shaped bore 34 having an upper terminal that is coaxial with the longitudinal axis of the main body member 12. The free end of the string 28 is threaded outwardly from the drum 20 through an aperture 37 in a housing wall 36 that is secured to the cap nut 30 and flange 23 of the drum. The string-is then guided around the exterior surface of the wall 36 for sub- ,stantially a full turn, whereupon it is directed around a vertically depending guide finger 39, and upwardly through a groove or indent 41 in the upper peripheral edge of the wall 36, for guidance into the J-shaped bore 34 of the upper end of the shaft 18.

It will now be recognized that by exerting an outward pull upon the free end of the string 28, the drum 20 will tend to rotate so as to enable additional string to move outwardly through the aperture 37, around the wall 36, upwardly around the guide finger 39 and through the provided bore 34. However, a brake assembly 43 is provided so as to control the amount of string thus-permitted to unwind from the drum. As is clearly shown in Figure 4, this brake unit 43 is of substantially inverted L-shape having the free end of one leg 44 threadedly carried by the shaft 18, while the other leg 46 extends downwardly along the outside of the main body member 12. The intermediate portion 47 between the angle legs 44, 46 is spring biased upwardly into frictional engagement with the lower surface of the radially outwardly extended flange 23 of the drum 20. This frictional engagement normally prevents rotation between the drum and the main body member 12. However, by pressing inwardly upon the outer leg 46 of the brake assembly, as shown in Figure 5, the brake 43 will be moved to the disengaged position 43a whereupon the intermediate portion 47 will disengage the lower surface of the flange 23, thus permitting the drum to rotate. By releasing the pressure upon the leg 46, the brake will again become engaged. The spring action of the duct-shaped brake unit 43 normally maintains the intermediate portion 47 thereof, in a brakeon position. The brake is moved to a brake-off position by depressing the depending leg 46 only when it is desired to lower the plumb bob to an approximate height. By then releasing the depending member 46, the brake is automatically returned to the brake-on position in which there is suflicient resistance to continued movement of the plumb bob to enable it to be placed in an exact finally adjusted position.

The string can be readily rewound upon the drum by drawing the rim 24 along any flat surface available, along the side of the operators leg, with the parts in the brakeon position, so as to prevent the drum from rotating in an unwinding position as the device is rolled back between strokes, thus insuring a tight and neat winding of the line upon the drum. The brake-on position of the parts also eliminates any back lash from developing during this rewinding operation.

One of the most important advantages of the present invention is that it is possible to obtain a minute adjustment of the position of the plumb bob-by turning the drum slowly between the fingers to bring the point of the weight extremely close to an existing point, or to a point to be marked. In using more conventional plumb bobs, such precise adjustment is diflicult, as it is necessary to adjust the position of the plumb bob from the uppermost end of the line that may be several feet away, thus making it difficult to control the plumb bob carried at the lower end of the line.

While this invention has been described with particular reference to the construction shown in the drawing, it is to be understood that such is not to be construed as im- .5 parting limitations upon the invention, which is best defined by the claims appended hereto.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. An adjustable plumb bob comprising, in combination, a weighted member having a point at one end, a drum rotatably supported adjacent to the opposite end of said weighted member, said opposite end of said member defining an aperture, a string secured at one end to said drum extending through said aperture, and a brake acting between said weighted member and said drum releasably preventing rotation therebetween for controlling the length of said string passing through said aperture, said drum being supported for rotation about the longitudinal axis of said weighted member, and said aperture being concentric with the longitudinal axis of said weighted member, said drum comprising a radially outwardly enlarged flange, said brake comprising an inverted L-shaped lever rotatably supported at the end of one leg upon said weighted member, the other leg of said lever extending downwardly along the side of said member, and the intermediate portion between said legs of said lever being frictionally engaged with an adjacent surface of said flange, and said intermediate portion of said lever being retractable out of frictional engagement with said adjacent surface of said flange in response to downward movement of said other leg of said lever.

2. An adjustable plumb bob as set forth in claim 1, further comprising a resilient rim secured to the periphery of said flange for rotation in response to a rolling movement thereof along a surface.

References Cited in the file of this patent UNTTED STATES PATENTS 2,784,498 Fleming Mar. 12, 1957 

